The present invention relates to a tightening device for cone belts and the like for use in cone belt transmissions, including at least one preferably driven cone belt pulley which is axially or substantially axially displaceable relative to at least one other, preferably driving cone belt pulley, and a cone belt interconnecting said cone belt pulleys, said tightening device engaging one run of the cone belt by means of a rotary member.
In cone belt transmissions where the driving and the driven cone belt pulleys are radially non displaceable relative to one another a tightening means is required to check that the desired cone belt tension is maintained. In case the driving as well as the driven cone belt pulley are non displaceable both radially and axially the arrangement of the tightening device involves no problem. In cases where one pulley, especially the driven one, is axially displaceable, a problem arises since--if a conventional tightening pulley or wheel is used--, the belt would be subjected to non-desirable bending and risk being pulled off.
In so-called ride-on lawn mowers the drive pulley is non displaceably fitted on the lawn mower frame and the driven pulley or driven pulleys are mounted on the cutter unit which is movable up and down either in a parallel motion or along the arc of a circle. The two runs of the cone belt will thus have to be able to swing like a pendulum about a point situated adjacent the drive pulley. The tightening device is as a rule placed so as to act upon the return run of the cone belt. To compensate for the movement of the cone belt run transversely of its longitudinal direction it has earlier been suggested that a spring-loaded cylindrical roller having a length exceeding the pendulum movement of the cone belt run should be used at the engagement point but it has been found that this would not function but the cone belt would engage at one and the same peripheral line of this roller and thus be subjected to heavy breakage in the transverse sense. The desired axial travel along the tightening roller has thus not been obtained.
The invention is based on the knowledge that it is preferable to subject the cone belt to guided bending of little extent while running out from the driven pulley, passing the tightening pulley and entering the drive pulley, and characteristic of the device according to the invention is that the tightening means includes a spring-loaded support lever arranged adjacent one of the cone belt pulleys and adapted to pivot about an axis situated substantially parallel with the cone belt pulley shaft and also about an axis oriented generally tangentially relative to said pulley, and that a tightening pulley preferably provided with a cone belt groove is fitted at a free end of said support lever in order to maintain the engagement of the tightening pulley independently of any displacement of the cone belt runs caused by the relative displacement of the cone belt pulleys.